1. Field of the Invention
The present invention relates generally to gear availability and synchronization indicator systems. More particularly, the present invention relates to gear availability and synchronization indicator systems that include selectively maskable displays.
2. Related Art
Heavy trucks generally employ manual transmissions having a relatively large number of gears. Such transmissions usually are non-synchromesh transmissions that require that the driven gears and driving gears be rotated at very nearly the same speed before they can intermesh. Thus, for any particular vehicle speed, it is necessary to match the engine speed with the vehicle speed for the particular gear selected before that gear can be engaged.
In order to match engine speed with vehicle speed for a given gear ratio, it is usually necessary to “double clutch” the transmission. This procedure involves first shifting the transmission into neutral and then adjusting the engine speed up or down to match the intended gear and then depressing the clutch and shifting the transmission into that gear.
Experienced truck drivers usually get a feel for what transmission gears are available under normal driving conditions and what engine speeds are necessary to engage these gears. This is frequently a matter of sensitivity to the sound of the engine in comparison with vehicle speed. Inexperienced operators, and even experienced operators in emergencies or under other stressful conditions (e.g., downhill acceleration), have difficultly in determining what gears are available for a particular vehicle speed.
A number of devices have been invented to assist the vehicle operator in shifting smoothly into the next higher or lower gear. For example, U.S. Pat. No. 5,941,922, to the present inventor, Kent Price (hereinafter the “Price '922 patent), which is hereby incorporated herein in its entirety, discloses a system which has become widely accepted by owners and operators of heavy trucks. In fact, the system disclosed in the Price '922 patent, sold under the tradename “Gearmaster,” has proven so effective in teaching, refining and maintaining gear shifting skills, that some truck driving instructors and fleet operators have expressed concern that drivers can become overdependent on the advantages provided by the '922 patent system, and may not consequently develop the skills required to operate heavy trucks without the Gearmaster system.
Thus, while the Gearmaster system has proven very effective, it has been problematic, in some circumstances, to utilize the Gearmaster system to the exclusion of traditional methods in that skills needed by operators to operate traditional heavy tucks without the Gearmaster may be underdeveloped or underpracticed.